Many products are often manufactured in a continuous web format for the processing efficiencies and capabilities that can be achieved with that approach. The term “web” is used here to describe thin materials which are manufactured or processed in continuous, flexible strip form. Illustrative examples include thin plastics, paper, textiles, metals, and composites of such materials. Illustrative examples of product components and products that are manufactured in a web format include adhesive tapes, reflective sheeting, optical films, packaging materials, labels, etc.
Such operations typically entail use of one or more, frequently many more, transport rolls (sometimes referred to as rollers) around which the web is conveyed throughout the manufacturing process undergoing a series of treatments, manufacturing steps, etc. Transport rolls are used for many purposes, including, for example, turning the direction of the web, positioning the web for travel through processing stations (e.g., coating and other treatment stations, converting stations, etc.), positioning multiple webs for lamination, stretching webs, etc. Rolls used in such operations are made of a variety of materials, with the selection dependent in large part upon the web(s) being handled, the operational parameters (e.g., speed, temperature, humidity, tension, etc.). Some illustrative examples of materials used to make rollers or covering surfaces thereon for transport of adhesive-sided webs include rubber, plastics, metal (e.g., aluminum, steel, tungsten, etc.).
Many web materials comprise an exposed adhesive layer on at least one side thereof. Conveying adhesive-sided web materials is challenging, particularly when the adhesive is tacky under the conditions in which it is being conveyed as the adhesive tends to stick to the surface of any transport roll it contacts, leading to fouling the roll, interfering with proper web conveyance, and degrading the web. One currently known handling technique is to coat idler rolls with low- or non-stick material. Although this may work satisfactorily for a time, the coating tends to wear off or become fouled and the rolls need to be removed from service and resurfaced, posing significant downtime and fabrication costs. Related approaches include wrapping idler roll with suitable low- or non-stick materials, (e.g., TEFLON™ Tape, TESA® 4563 or 4863 Tape (silicone rubber coated rayon tape), silicone tape, etc.), or applying sleeves of suitable low- or non-stick materials over the idler roll. Such approaches are still subject to undesirable downtime and handling expenses. Another technique is to knurl the surface of an idler roll so as to reduce its area of contact with the adhesive side of the web as it is conveyed past. This approach is typically successful only when using relatively lower tack adhesives. Still another technique is to use a removable protective liner on the adhesive surface during conveying the material. Use of liners necessitates additional material and processing costs.
Many similar challenges and solutions are encountered with conveying rigid articles having exposed adhesive layers.
In order to provide desired end use performance, current trends include the use of pressure sensitive adhesives in relatively thicker coatings, pressure sensitive adhesives that are more aggressively tacky, have lower viscosity, etc. Such adhesive materials are more difficult to handling during manufacturing of the intended adhesive-sided product.
The need exists for improved methods and apparatus for conveying articles having an exposed adhesive layer.